Mod_perl installations: 4.6 million hostnames, 460k unique ips.
Java Servlet engine installations: 295k hostnames, 37k unique ips
Different data point, the security space module report (for java look for "mod_jk", "Resin" and "ApacheJServ").
Yes, I realize there are all sorts of reasonable and unreasonable explanations for these numbers, but it's still fun.
Web Server Survey from Netcraft and Security Space. Apache is well over 60% now.
